Seriously, can you imagine a thirteen year old go off in class when pushed by a bully."I smite you with the Emperors fury!" "There is only war!" "Die Heretic!" "Tyranids are coming, Tyranids are coming!" "Don't tell Matt Ward I want a new Ultramarines rulebook...!".

That thirteen year old would be the hero of his people, he would grow up to become the Emperor, he will die at the hands of Matt Wa-HORUS! and manage to make his race to piss off every race in the known galaxy.

clearly you don't know that many thirteen year old boys. It would've gone like this: "I know. I know. I know. We'll have orc in space! And we'll have them talk like soccer huligans, and they have to fight against these Space Marines who look like knights and speak in posh british accents."